This is such an interesting question. I would start by saying that I think it is clearly wrong to target someone who isn't in their right mind, either because they are grieving the loss of a loved one, are elderly, mentally disabled, etc. While I generally believe it is the seller's responsibility to be educated on the value of what he or she is selling, in some situations they aren't able to, and that is when you should absolutely step up and make a fair offer.
However, when the seller is perfectly capable of making an informed and rational decision, I think the notion of offering the seller at or close to wholesale when they wanted less is completely absurd. It is trivial to do a Google search and find resources like DNJournal, Estibot, NameBio, NamePros, etc. and at least get a basic education on domain values. Someone being uninformed with so much information a click away is not your responsibility. If they were too lazy to do their homework, why should you give them the benefit of years of experience and knowledge, not only for free but pay them for it? That makes no sense. Information asymmetry and inefficient markets is the basis for this entire industry and many others. Your knowledge cost you time, and money from bad buys, to acquire.
Then there is this notion of paying them at or close to wholesale value. If any of you can predict the price of all the auctions closing every day within even 20% you are a unicorn. Because pricing is fairly subjective and somewhat unpredictable, how do you determine when someone is being unethical and taking advantage?
Maybe there's a domain that I think would wholesale at $10k so I offer $7.5k trying to be fair, even though the seller only asked for $2.5k. Then other people think it would wholesale for $20k and they judge me for taking advantage. Maybe we're all wrong and it ends up wholesaling for $5k, and I feel pretty stupid when the seller only asked for $2.5k but I tried to "do the right thing" by negotiating against myself. At the end of the day if the seller is happy with the price (and is mentally sound), and you're happy with the price, it is insane to give them more than they want. Pay the $2.5k and move on.
Diving even deeper into the situation above, what percentage am I allowed to earn in profit from my knowledge before I am taking advantage of someone? Only 10%, or is it 50%, or can I double my money, or triple it? Who is on the panel of domain ethics to decide what is a fair reward for my work, my years of experience, the risk I take in buying the domain, etc. Am I allowed to lowball someone harder than a newbie because my time is more valuable and I should get a higher return for my experience? Or should a newbie be allowed to lowball someone harder than me because I should be more confident in my valuation skills, so the risk is lower and thus the reward should be as well?
And what about situations of a distressed seller who needs quick cash, or someone who doesn't care and just wants to sell the name and move on? I'm reminded of a recent DomainSherpa interview where Drew picked up Inertia.com for $5k. Was he unethical for offering that amount when the other Sherpas thought it was worth 4-5x that wholesale, and should he have changed his mind and offered five-figures even after the seller agreed to $5k? By some of your arguments he is unethical for not doing that.
However it turns out the owner turned down several offers of $50k, an offer of $100k a long time ago, etc. So he was well aware of the potential, but was still happy to just take the cash and run. But if Drew had "done the right thing" and said "nevermind, I started too low and it is worth more, I'll give you $15k instead"... the seller would gladly take it and Drew would be an idiot. You can't always know the situation when you're walking into it, so all you can do is offer a price that you're happy with, and find the intersection where the seller will be happy with the price too.
It's such a gray area that I don't think there is room to judge people. And I would imagine that many of those passing judgements in this thread, when seeing someone post an LLL.com for $5k on the forums would be fighting and clawing their way to be the first to post "SOLD" rather than the first to post "Hey, that's too low, you should be charging more!"
I'd like to put out three hypothetical situations:
Imagine you reach out to a Fortune 500 company who owns a nice domain, and they agree to sell it to you for a price that you are sure is well below wholesale value. Do you move forward with it? I think most would, rather than saying "Hey super rich company, I'd rather give you even more money and earn less myself." After all they have the resources and the wherewithall to determine the value, so if they don't, well... seller beware. Maybe the person at the company who made the deal ends up getting fired because of it, when a higher-up catches wind of it and sees it as a huge mistake. Is that your fault? Maybe the higher-ups don't know domain values either and the person gets a promotion for bringing in revenue for an unused domain. Who knows, and I don't think that is your responsibility to do their job for them or try to divine what a future outcome might be.
Now for the second situation. Same as above but it is a large, well-funded charity selling it. What do you do? Personally this one would give me pause because the money would be going to help people in need. But if you take away the emotion, it's really not much different from the situation above. They had the same ability to determine the fair value but didn't. Maybe they are the ones being unethical by not being informed and making sure they maximize the value of their assets. Not sure I would be able to sleep well if I did this, but I wouldn't judge someone as unethical if they did.
The third situation is that you're selling a domain to an end user, and their first offer is double what you thought you could get for it retail. Do you say "Hey, I think you offered too much, the domain is worth less than that. You should go research domain values and get back to me"? Heck no, you either take the money and run, or try to work them up even higher. That's business, and a domain is worth the intersection of what the buyer is willing to pay and the seller is willing to receive.
I've said it before and I'll say it again, the same domain in my hands is worth less than in Schilling's hands, because he has the experience and wherewithal to demand more. It's no different on the flip side, if someone owns a domain and isn't experienced in putting a value on it, that domain is worth less.
And again, who is to say what the value really is, how much profit you can make before you're taking advantage, whether or not the seller should have had the ability to determine the value, etc.? Many, many shades of gray here.
I do know one thing for certain, if I owned something that I wasn't familiar with, let's say a baseball card, and I undersold it, my first reaction wouldn't be "Hey that buyer scammed me!" it would be "Dang, I should have taken five minutes to figure out what it was worth."
Sorry for the essay, I just think this is a really interesting topic.